This invention relates to raster scanned cathode ray tubes and more specifically to electronic circuits for controlling the raster scan deflection of cathode ray tubes for displaying arbitrary forms thereon.
Raster scanned cathode ray tubes (CRTs) have been utilized to display a variety of pictures and forms in response to modulated video display signals in televisions and oscilloscopes, for example. In special use CRTs, such as in avionics equipment and medical technology displays, a need has been observed to display both constant forms and varying data and forms in response to changing conditions. The constant forms may be required to be generated essentially simultaneously with the varying data, or may be generated as a "framework" around which the varying data is displayed relative to the constant forms.
One problem which has been observed is the expensive memory capability required to store the software necessary to display these constant forms when utilizing a digitally-operated and microprocessor-controlled cathode ray tube.